Ester-base lubricant containing non-corrosive ep agent



V 2,865,755 Patented Dec. 30, 1958 dice ESTER-BASE LUBRICANT CONTAINING NON-CORROSIVE EP AGENT Raymond B. Tierney, Beacon, and Robert H. Krug, Cornwall, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application May 31, 1955 Serial No. 512,304

9 Claims. (Cl. 252-475) This invention relates to a lubricating composition which is particularly designed for lubrication of turbines used in aircraft, particularly in turbo-prop and turbojet planes. More particularly, this invention discloses a lubricating composition containing an EP and antiwear'additive which does not adversely affect the oxidation and corrosion properties of the lubricating composition.

Mineral oil base lubricants are not satisfactory for lubrication of turbines used in jet engines which operate over a wide temperature range and usually under severe operating conditions. Specially formulated lubricants which have thermal stability, oxidation stability, good EP and anti-Wear properties and a high viscosity index are required for lubrication of turbo-jet and turboprop engines. The requirements for a lubricating oil for turbo-prop and turbo-jet engines are set forth in MIL-L-7808B. Up to the present time, only ester-base lubricants have met these requirements.

The lubricant composition of this invention comprises a diester or a polyester as the major component and di(o-chlorophenyl) phenyl phosphate in an amount sufficient to impart EP and anti-wear properties to said lubricant composition. The di(o-chlorophenyl) phenyl phosphate usually constitutes 0.5 to 5 weight percent of the lubricant composition and materially improves the EP and anti-wear properties of the ester-base lubricant without adversely alfecting its oxidation and corrosion properties.

It is well known in the art that phosphate esters, particularly aryl phosphates and halo-substituted hydrocarbon phosphates, are EP agents. Tricresyl phosphate, tris-tri-chloropropyl phosphate and tri(p-chlorophenyl) phosphate are known to possess EP properties. Of all the aryl and halo-hydrocarbon substituted phosphates tested, di(o-chlorophenyl) phenyl phosphate is unique in its action in imparting the desired EP and anti-wear properties to an ester-base lubricant without adversely aifecting its oxidation and corrosion properties. Other hydrocarbon phosphates and halo hydrocarbon substituted phosphates, even though thty are closely related to di(o-chlorophenyl) phenyl phosphate in chemical constitution, were either ineffective in imparting the desired EP and anti-wear properties or seriously degraded the oxidation and corrosion properties of the ester-base lubricants. The unique action of this compound in a particular environment of an ester-base lubricant is entirely unexpected since there is no analogous action in mineral oil base lubricants.

Di(o-chlorophenyl) phenyl phosphate has the follow- 7 ing structural formula:

. or more carbon atoms.

It is recommended that this compound have a Neut. No. less than 5.0 and preferably less than 2.0 in order to formulate lubricant compositions of the desired oxidation and corrosion properties. In a copending application Serial No. 512,305, filed of even date in the names of Raymond B. Tierney and Robert H. Krug, a novel method of treating di(o-chlorophenyl) phenyl phosphate to yield a product of low Neut. No. is dis closed. The method of the copending application involves contact of the di(o-chlorophenyl) phenyl phosphate under anhydrous conditions with anhydrous alkali metal carbonate at a temperature less than F. The lubricant composition of this invention contains the di(o-chlorophenyl) phenyl phosphate in an amount sufficient to improve its EP and anti-wear properties. The desired improvement in EP and anti-Wear properties is effected by use of between 0.2 and 5 weight percent of di(o-chlorophenyl) phenyl phosphate. The usual concentration of the EP additive of this invention is between 1.0 and 3.0 percent.

The most commonly used ester base is an aliphatic diester of an organic dicarboxylic acid. The dicarboxylic acid component is usually an aliphatic dicarboxylic acid containing 6 to 12 carbon atoms but glutaric acid esters and succinic acid esters may also be used. From the standpoint of cost and availability, the preferred dibasic acids are adipic acid, sebacic acid and azelaic acid. The aliphatic alcohols used to form the diesters usually contain at least 4 carbon atoms and may contain 20 C to C alcohols are most commonly used. Ether alcohols such as Cellosolve and carbitol may also be used in the formation of the aliphatic diesters of organic dicarboxylic acids used as the lubricating base in the compositions of this invention.

Specific examples of the dialkyl esters of aliphatic dicarboxylic acids, which are the preferred reagents for use in the lubricant compositions of the invention, are as follows: di-Z-ethylhexyl sebacate, di-2-ethylhexyl azelate, di-Z-ethylhexyl adipate, dilauryl azelate, di-sec-amyl sebacate, di-Z-ethylhexyl alkenylsuccinate, di-2-ethoxyethyl sebacate, di-Z-(Zmethoxyethoxy) ethyl sebacate, di-2-(2ethylbutoxy) ethyl sebacate, di-Z-butoxyethyl azelate, di-2-(2butoxyethoxy) ethyl alkenylsuccinate, etc.

In addition to the aliphatic dicarboxylic acid esters described above, polyester lubricants formed by a reaction of an aliphatic dicarboxylic acid, a glycol and a monofunctional compound, which is either an aliphatic monohydroxy alcohol or an aliphatic monocarboxylic acid, in specified mol ratios are also employed as the synthetic lubricating base in the compositions of this invention; polyesters of this type are described in U. S. 2,628,974 on Polyester Synthetic Lubricants, which issued to R. T. Sanderson on February 17, 1953. Polyesters formed by reaction of a mixture containing specified amounts of 2-ethyl-1,3-hexanediol, sebacic acid and 2-ethylhexanol and by reaction of a mixture containing adipic acid, diethylene glycol and Z-ethylhexanoic acid illustrate this class ofsynthetic polyester lubricating bases.

Polyesters formed by reaction of a monocarboxylic acid and a glycol may also be used as the ester component. The acid component is usually an aliphatic acid containing at least 6 carbon atoms. component is advantageously a straight glycol such as 1,6-hexanediol, but ether glycols, such as tetraethylene glycol, may also be used.

Specific examples of the diesters of glycols are the following: di-n-decanoate of 1,4-butanediol, di-2-ethylhexanoate of 1,6-hexanedio1, dilaurate of 1,4-hexanediol, dioctanoate of 1,5-pe'ntanediol, dilaurate of tetraethylene glycol, dilaurate of triethylene glycol, dioctoate of pentaethylene glycol.

The glycol The sulfur analogs of the above-described esters are also used in the formulation of the lubricating compositions of this invention. Dithioesters are exemplified by di-Z-ethylhexyl thiosebacate, di-n-octyl thioadipate and the dilaurate of 1,5-pentanedithiol; sulfur analogs of polyesters areexernplified by the reaction product of adipic acid, thioglycol and 2-ethy1hexyl mercaptan.

The finished lubricant composition of this invention normally contains other well known additives which act as V. I. improvers and anti-oxidants. For example, phenothiazine, which acts as an anti-oxidant and a methacrylate polymer, which acts as a V. I. irnprover, are usually includedin the finished lubricants and are often necessary in order to meet the rigid requirements of MIL-L-7808B. Phenothiazine, which has the formula is a particularly eflective anti-oxidant and anti-corrosive agent. Phenothiazine inhibits corrosion by preventing oxidation of the components of the lubricating composition to acidic bodies which are inherently corrosive in nature. Phenothiazine is usually present in a concentration of 0.1 to 1.5 weight percent-of the lubricant composition.

Methacrylate polymers are well known V. I. improvers and pour point depressors. Polyester base lubricants, althoughthey, .perse, possess excellent V. I. and pour, usually require the presence of small concentrations of methacrylate polymers to meet the rigid requirements of MIL-L-7808B. These methacrylate polymers are usually copolymers of two or more esters of methacrylic acid and usually have'a molecular weight between 10,000 and 20,000. The methacrylateesters have the following general formula:

CH; [-CH:.-] 0 R whereinR is an aliphatic radical. Copolymers which find particular use as V. I. improvers and pour point depressants are the following: a copolymer wherein Rin the above formula comprises20% lauryl, 40% octyl and 40% cetyl; a copolymer wherein R in the above formula is 50% stearyl and 50% lauryl; a copolymer wherein R in the above formula comprises 50% lauryl and'50% octyl.

Methacrylate polymers are usually sold in the form of aconcentrate comprising approximatcly50% polymer and50%'carrier oil. Forthe lubricant compositions of this invention, ithas beenfound advisable to use an ester-type carrier oil rather than the usual mineral base lubricatingoil. The use of a methacrylate ester in an ester-type carrier oil has proven particularly effective in having two nitrogen atoms attached directly to different carbon atoms ofthe same open chain, are also sometimes incorporated in the finished lubricant. Compounds of this typewhich generally constitute'0.05 to0.6 weight percent of the, composition actas metal. deactivators as disclosed in theDowning et al., No. 2,282,513. A preferred compound of this class, which is commercially available, is disalicylal propylenediamine which is also known as disalicylidene-1,2-diaminopropane. This compound is sold undcr the trade name DMD by E. I. Du Pont de Nemours and Company and as Tenarnene 60 by Tennessee Eastman. Examples of other compounds of this type are the following:

Di-(2-hydroxy-3-methoxybenzal) ethylenediamine Di-(Z-hydroxybenzal) ethylenediamine Di-(Z-hydroxybenzal) decamethylenediamine Di-(Z-hydroxybenzal) triethylenetetramine Di-(Z-hydroxybenzal) hexamethylenediamine DMZ-hydroxybenzal) 1:3 propylenediamine Dibenzal ethylenediamine Dibenzal hexamethylenediamine Dibenzal diethylenetriamine Dibenzal triethylenetetramine Disalicylal ethylenediamine The four-ball mean Hertz load test is used as a test for screening EP and anti-wear agents. Avalueabove 35 in this test is necessary in order to mark acompound of interest as an EP and anti-wear agent for polyester base lubricants. In Table I there are shown the results obtained by'incorporation of various phosphate and halohydrocarbon phosphate esters in a base oil comprising approximately 96.5 percent di-isooctyl adipate and 0.5 percent phenothiazine.

TABLE I Four bull menu Hertz load test,,kg.

Base nil Base oil+3% tricresyl phosphate 32 Base oil+3% tri(p-chlorophenyl) phosphate 25 Base .oi1+3% diphenyl-o-chlorophenyl phosphate." 29 Base oil+3% di-(fi-chloroethyl) 2-ethylhexyl phosphate 35 Base oi1+3% tris(trichloropropyl) phosphate 38 Base oil+3% bis(o'chlorophenyl) phenyl .phosphate 40 .thefformation of tri(o-chlorophenyl) phosphate. The superiority of di(o-chlorophenyl) phenylphosphate over all the EP and anti-wear agents tested is also significant.

In Table II there are shown the results of subjecting the ester lubricants containing the three EP agents which passed the screening test in Table I in the oxidationcorrosion test of MILL-7808B. The base oil was the same used in Table .1, namely comprising 96.5 percent di-isooctyl adipate, 0.5 percent phenothiazine; 3% EP agent was used in each test.

TABLE II Di (o-chlor- Di (fi-ehlor- Tris-(tri- Oxidation-Corrosion MIL-L- Ophenyl) oethyl)2- chloro- Test (347 F./72 Hr.) 7808B phenyl ethylhexyl propyl) Spec. phosphate phosphate phosphate mg./sq. 0111.:

Cu i0. 4 0.0 .2. 0 5. 5 i0. 2 .0. 0 +0. 2 +0. 1 1:0.2 0:0 -4;0 -11.2 i0. 2 0.-0 +0. 2 +0.1 i0. 2 0.0 +1.2 +0. 6

The data in the above table clearly indicate that di(fichloroethyl) Z-ethylhexyl phosphate and tris(trichloropropyl) phosphate degrade the oxidation-corrsion properties of an ester-base lubricant to a serious degree. In contrast, di(o-chlorophenyl) phenyl phosphate completely meets the rigid requirements of the oXidatiori-corrosion test of MIL-L-7808B, demonstrating thatit alone of all the phosphate and halo-phosphate esters tested provides a high level of EP and anti-wear properties without de- 6 Example IV V A blend was prepared having the following composition:

Percent by weight grading the oxidation and corrosion properties of ester- 5 Di-Z-ethylhexyl sebacate 79.5 type lubricants designed for lubrication of turbo-prop Polymer of butyl methacrylate in di-Z-ethylhexyl and turbo-jet engines. sebacate (40% concentrate) 18.0 The formulation of finished lubricants containing the Di(o-chlorophenyl) phenyl phosphate 2.0 HP additive of this invention is illustrated in the follow- Pheflolhlallne ing examples. The properties of this blend are shown in Table IV.

TABLE HI Examples MILL-7808B limits I II III Flash 000 "F 350 min. 41 Kin. Vis., est, at: 405 0 460 210:1 3.0 (min.) 4.60 4.70 7. 63 F l'totl ltll 5 2522 122 max Viscosity stability (3 hr. at 65 F.), percent =l=3 (max.) +1. 9 +0. 4 0.3 Pour Point, F 76 (main) 75 --75 75 Foam Test, Seq. 1, 2, 3 ml 100-25-100 max. -0-0 10-10-20 0-20-0 Panel Coking Test, 600 F./8 Hrs., mg 100 (max.) 23 37 49 Evaporation, 400 F/fik Hrs, percent 50 (max) 12.1 12.9 8.3 22. 7 18.0 "15 Rubber Swelling, per n 12-35 21 8 22. 7 18.0 .6 1 .2 Corrosion, 450 F/50 Hr. mgJsq. in.: 22 8 S3858! Emax.) 0. 1g 0. 7 0.0 80D Load Corrosion, 325 F./1 Hr., MgJsq. in 6 1113 3. 0. 2 2 Corrosion and Oxidation stability, 347 F./72 Hrs, wt.

change, mg./sq. cm.:

on =e0.4 0. 4 0. 0 0. 0 Al :l:0.2 0. 0 0. 0 0. 0 M 5:02.. 0. 0 0. 0 0. 0 85 88 -2 0. Vis. Inc., 100 F., percent 5 to +15 +1. 6 0. 91 2. 8 Total Acid N 0. In 2.0 (max) 0. 9 0. 95 0. 3

Example I A blend was prepared having the following composition:

Percent by weight Di-isooctyl azelate 95.3 Copolymer of 50% lauryl methacrylate and 50% stearyl methacrylate in a di-Z-ethylhexyl sebacate base oil (50% concentrate) 2.0 .Di-(o-chlorophenyl) phenyl phosphate 2.0 Phenothiazine 0.5 Disalicylidene 1,2-diaminopropane 0.2

The properties of this product are shown in Table III.

- Example II A blend was prepared having the following composition:

Percent by weight Di-isooctyl azelate 95.5 Copolymer of 50% lauryl methacrylate and 50% stearyl methacrylate in a di-Z-ethylhexyl sebacate base oil (50% concentrate) 2.0 Di(o-chlorophenyl) phenyl phosphate 2.0 Phenothiazine I 0.5

The properties of this blend are shown in Table III.

Example III Di(o-chlorophenyl) phenyl phosphate ....do.... 2.0

Phenothiazine do 0.5

Kerosine concentrate of 10 weight percent dimethyl silicone p p. m-.. 150

The properties of this blend are shown in Table III.

The data in Table III indicate the superior turbine lubricants which are formulated using the extreme pressure additive of this invention. The compositions of Examples I, II and III, meet the rigid requirements of the MIL-L-7808B specification from the standpoints of extreme pressure and wear properties and of oxidation and corrosion resistance.

In Table IV there is shown the properties of the high viscosity composition of Example 4, which was formulated to meet the requirements of a British specification for jet engine lubricants wherein the viscosity requirements are substantially higher than they are in the U. S. military specification.

TABLE IV Example 4 Kim Vis. at: Compositions Pour point -.-75. Flash 430.

Vis. stab., 65 F Foam test, Sq. l, 2, 3 30; 30; 30. Panel coking test, 600 F./8 hr., mg 29.

Evap., 400 F./6 /2 hr., percent 10.3.

H rubber swell, percent Corr. 450 F./ 50 hr., mg./sq. in.:

Ag 0.3. SOD Pb corr Oxidation-corrosion test,

Cu +0.0 stain.

Al 0.0 stain.

Mg 0.1 stain.

Fe 0.0 stain.

Ag 0.0 stain. Vis. inc., percent 1.8.

Neut. no. inc 0.68,

The high viscosity product,who'se properties are shown in Tablc'r'ly, meutslthe extreme pressnre; :weacandmxirlai tion-corrosion requirements of MIL-L-7808B. It is noteworthy *that 'di(b-chlorophenyl) phenyl phosphate is effective as an EP and anti-wear agentdn a wide varietyof ester base lubricants. L k

Obviously, many modifications"andwvariation of the invention, as hereinbefore -set forth; may bc ma'cle without departing from the spirit and scop e thereof and there-m hon atoms."

phenyl phosphate.

4. A lubricant composition'consi'stin'g essentially'of an aliphatic di-carboXylic"'acid ester of lubricating oil characteristics, 0.2 to 5 weight percent di(o-chlorophenyl) of an aliphatic 20 3. A lubricant composition according-{to claim -1 con-' taining. 0.2 to 5 weight pcrcent'tofxdi(ochlorophenyl) phenyl phosphate, an oxidationinhibiting amount of-- phenothiazineand a methacrylate polymer in 'aV. I. im-.-

proving amount.

5. A lubricant composition according to claim 4 con- 9. A lubricant c taining between "1.0 to 3.0' weighbpercent :di(o-chloro-i: phenyl phenyl-phosphatep 0.15 10 1.5. percent 1phenothia-w zinc; and 1.5 to 8 weight percent imethacrylate:polymer;i

6. A ..lubricant rcomposition according' 'ito :claim 54 in which'themajorucomponentwis a diOctyIEsebacater 7 A :lubricant composition according .to claim 4 in which the major component is a dioctylazelate.

8. A lubricant composition.accorciingto claim ;.4 in which the major component ds a=dioctyl adipate ester having lubricating characteristics, 1 to 3 weight percent di(o-chlorophenyl) phenyl phosphate, 0.1 to 1.5 percent phenothiazine, 1.5 to 8 weight percent methacrylate polymer, and 0.05 to 0.6 weight percent disalicylidene, 1,2-diaminopropane.

keferenc esfffiteil fiii the file of this patent znosgss 1.- 1935 2,282,513 1942 2529,190 1950 2,542,604 1951 OTHER REFERENCES fsymposiumidn.Syiithetic Lubricants, A. S. T. M. Tech. Pub No.; 77 1947), page 23.

Davey} The Mechanism of Action of E. P. Agents,

Scientific Lubricationpseptember 1949, pages 7-14.

omposition consisting essentiallyiof a dialiphatic ester of an organic dicarboxylic 'acidfsaid 

1. A LUBRICANT COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF AN ALIPHATIC CARBOXYLIC ACID ESTER OF LUBRICATING OIL CHARACTERISTICS AND DI(O-CHLOROPHENYL) PHENYL PHOSPHATE IN AN AMOUNT SUFFICIENT TO IMPART EP AND ANTI-WEAR PROPERTIES TO SAID COMPOSITION. 